Salidroside protects pulmonary artery endothelial cells against hypoxia-induced apoptosis via the AhR/NF-KB and Nrf2/HO-1 pathways

Background: The apoptosis of pulmonary artery endothelial cells (PAECs) is an important factor contributing to the development of pulmonary hypertension (PH), a serious cardio-pulmonary vascular disorder. Salidroside (SAL) is a bioactive compound derived from an herb Rhodiola , but the potential protective effects of SAL on PAECs and the underlying mechanisms remain elusive. Purpose: The objective of this study was to determine the role of SAL in the hypoxia-induced apoptosis of PAECs and to dissect the underlying mechanisms. Study design: Male Sprague-Dawley (SD) rats were subjected to hypoxia (10% O 2 ) for 4 weeks to establish a model of PH. Rats were intraperitoneally injected daily with SAL (2, 8, and 32 mg/kg/d) or vehicle. To define the molecular mechanisms of SAL in PAECs, an in vitro model of hypoxic cell injury was also generated by exposed PAECs to 1% O 2 for 48 h. Methods: Various techniques including hematoxylin and eosin (HE) staining, immunofluorescence, flow cytometry, CCK-8, Western blot, qPCR, molecular docking, and surface plasmon resonance (SPR) were used to determine the role of SAL in rats and in PAECs in vitro. Results: Hypoxia stimulation increases AhR nuclear translocation and activates the NF- K B signaling pathway, as evidenced by upregulated expression of CYP1A1, CYP1B1, IL-1 (i , and IL-6, resulting in oxidative stress and inflammatory response and ultimately apoptosis of PAECs. SAL inhibited the activation of AhR and NF- K B, while promoted the nuclear translocation of Nrf2 and increased the expression of its downstream antioxidant proteins HO -1 and NQO1 in PAECs, ameliorating the hypoxia-induced oxidative stress in PAECs. Furthermore, SAL lowered right ventricular systolic pressure, and decreased pulmonary vascular remodeling and right ventricular hypertrophy in hypoxia-exposed rats. Conclusions: SAL may attenuate the apoptosis of PAECs by suppressing NF- K B and activating Nrf2/HO-1 pathways, thereby delaying the progressive pathology of PH.